This project seeks to determine whether the regulation of lens fiber differentiation and maturation is associated with alterations in the plasma membrane. To this end, the principal lipid and protein components of embryonic and adult chicken lens membranes are being identified, and their metabolism is being investigated. Because of the known involvement of phosphatidylinositol (PI) turnover and phosphatidylethanolamine (PE) transmethylation in regulatory mechanisms in other cell types, this study has focused on lens phospholipid metabolism using isotopic labeling techniques and computer modeling to analyze the kinetics of radio-isotope incorporation. The relationships between phospholipid metabolism and differentiation have been studied in vitro, under defined conditions, using explants of embryonic chick lens epithelia. These tissues differentiate to form lens fibers in the presence of fetal calf serum, insulin, or vitreous humor. Results obtained in vitro have been compared with results obtained in vivo in lenses of embryonic chicks and other species.